There are a multiplicity of known methods for producing multicoat color and/or effect paint systems (also called multicoat finishes). The prior art (compare, for example, German patent application DE 199 48 004 A1, page 17, line 37, to page 19, line 22, or German patent DE 100 43 405 C1, column 3, paragraph [0018], and column 8, paragraph [0052], column 9, paragraph [0057], in conjunction with column 6, paragraph [0039], to column 8, paragraph [0050]), for example, discloses the following method, which involves                (1) applying a pigmented aqueous basecoat material to a substrate,        (2) forming a polymer film from the coating material applied in stage (1),        (3) applying a clearcoat material to the resultant basecoat, and subsequently        (4) curing the basecoat together with the clearcoat.        
This method is widely used, for example, for the original finish (OEM) of automobiles and also for the painting of metal and plastic parts for installation in or on vehicles. The present-day requirements for the technological qualities of such paint systems (coatings) in application are massive.
A constantly recurring problem and one still not resolved to complete satisfaction by the prior art is the mechanical resistance of the multicoat systems produced, particularly with respect to stonechip effects.
The qualities of the basecoat material, which is particularly important in this context, and of the coats produced from it are determined in particular by the binders and additives—for example, specific reaction products—present in the basecoat material.
A further factor is that nowadays the replacement of coating compositions based on organic solvents by aqueous coating compositions is becoming ever more important, in order to meet the rising requirements for environmental compatibility.
The problem addressed by the present invention was therefore that of providing a reaction product which can be used to produce coatings that no longer have the disadvantages referred to above in the prior art. More particularly, the provision of a new reaction product and the use thereof in aqueous basecoat materials ought to create the opportunity for provision of coatings which exhibit outstanding adhesion qualities and very good stonechip resistance and which at the same time can be produced in an eco-friendly way through the use precisely of aqueous basecoat materials.